Safety steering columns are used in motor vehicles to increase driver safety during frontal impacts. The safety steering column prevents parts of the steering column, and, in particular, a steering wheel from being pushed into a driver's compartment. To achieve this, various, generally passive mechanisms are known. One approach is to configure the steering column as a telescopic steering column. which a part of the steering column engages in another part of the steering column, and, if a predefined threshold force is exceeded, can be pushed telescopically therein, whereby the total length of the steering column is reduced. The two parts may for example be connected via a connecting element, which is designed to yield when the threshold force is exceeded.
Alternatively or additionally, crumple elements may be provided, which deform under a force above a threshold value, and are compressed in the longitudinal direction of the steering column. In this way, as well as an effective shortening of the steering column, energy absorption is achieved. While a corresponding crumple element should yield reliably under the effect of a sufficiently strong axial force, at the same time transmission of a torque within the steering column must be guaranteed. For this, either the crumple element must be sufficiently, torsionally rigid against torque, or torque must be transmitted via other components.
Modern safety steering columns are functionally effective, but often complex in construction, and consist of a plurality of interacting components. These increases cost and time for construction. Also, a high number of components and complexity make possible repairs to the steering column expensive and complicated.
EP 0 091 671 A2 discloses a safety steering column with a rigid steering column portion and a tubular part with a grid structure that yields on crushing of the steering column. The tubular part together with the steering column portion is made integrally from fiber-reinforced plastic. The grid structure may be formed in particular by webs that cross each other and run at an angle of 55° to a longitudinal axis of the tubular part.
U.S. Pat. No. 4,465,301 A discloses a safety steering column into which an approximately tubular safety element is inserted, which consists of mutually crossing strands of fiber-reinforced plastic and may for example have a round or octagonal cross-section. It is provided that the safety element is compressed in the longitudinal direction in an accident, while it resists torque on steering movements.
GB 1 125 206 A presents a safety steering column in which a generally tubular safety element with an interrupted structure of metal is provided. Here, either helical metal strips wound in opposing directions are welded together, or a tube is made from an interrupted plate. A similar safety column is disclosed in U.S. Pat. No. 3,500,698 A.
U.S. Pat. No. 4,634,399 A describes a component for transmitting torque between two shafts, e.g. inside a steering column. A grid-like sheath is arranged at a distance around a continuous core. The sheath is made of mutually crossing strands of fiber-reinforced plastic.
WO 2015/053940 A1 describes a component that may be used e.g. in aircraft or motor vehicles. To reduce stresses and achieve improved energy absorption, it is provided that the component is produced in an additive production process with an interrupted inner structure. This inner structure is produced integrally with the outer parts of the component.
WO 2015/164663 A1 discloses an energy-absorbing cell with a first structural element and a second structural element spaced from, and oriented parallel to, this. The structural elements are connected via intermediate elements that are arranged at an angle to each other. The energy absorption is primarily achieved by deformation of the intermediate elements. By repeating this cell structure, energy-absorbing parts of different sizes can be produced, in particular by additive production methods.
Also, in the prior art, various safety steering columns are known that are based on two telescopically intermeshing steering column parts, substantially in the manner of a telescopic steering column, whereby the telescoping of the two parts together deforms an energy-absorbing element.
Thus U.S. Pat. No. 3,401,576 A shows a safety steering column with two telescopically intermeshing parts that are surrounded as a whole by a sleeve of metal formed in a corrugated tube, which is compressed with energy absorption in an event of an accident.
U.S. Pat. No. 3,461,740 A describes a safety steering column with a coupling arrangement in which a first part, remote from the steering wheel, engages with a frustoconical end in a second part on the steering wheel side. If an axial force between the two parts exceeds a specific threshold value, the first part is pressed into the second part, deforming the latter, whereby the steering column is shortened.
U.S. Pat. No. 3,590,655 A discloses a safety steering column with different energy absorption units. In a first energy absorption unit, a plurality of balls is arranged between two cylindrical elements arranged concentrically to each other. In a second energy absorption unit, a cylindrical element has a grid-like interrupted portion that is constructed from mutually crossing strip portions.
U.S. Pat. No. 3,740,068 A presents a safety steering column in which two parts again intermesh telescopically, wherein an externally arranged energy absorption element is constructed from partially interrupted, angled sheet metal parts.
A safety steering column disclosed in U.S. Pat. No. 3,835,725 A comprises an upper and a lower portion, which intermesh telescopically, and are connected together via a concentrically arranged metal tube. When an axial force between the two portions exceeds a limit value, the metal tube is compressed and deforms, and the portions are pushed into each other.
U.S. Pat. No. 4,411,167 A presents a safety steering column in which two parts of the steering column are coupled together via a plurality of elements, partially intermesh telescopically and are connected together by plastic rods. When a specific axial force is exceeded, the respective plastic rod breaks off and the elements are pushed into each other. Finally, complete separation of the two parts from each other is also possible.
In a safety steering column disclosed in U.S. Pat. No. 7,644,951 B2, an inner tubular part engages in an outer tubular part. The inner tubular part has a widened portion at an axial distance from the outer tubular part. Between this portion and the outer tubular part, the inner tubular part is surrounded by a plastic tube that deforms when an axial force exceeds a threshold value, wherein the inner tubular part is pushed into the outer tubular part.
U.S. Pat. No. 5,342,091 A discloses a safety steering column in which a solid inner part engages in a tubular outer part. A pin is pushed through a transverse bore of the inner part and protrudes on both sides, supporting a tubular energy absorption element. If the inner part is pushed into the outer part, the energy absorption element comes into contact with the outer part and is stopped by this, wherein the pin is pushed to inside with deformation of the energy absorption element.